Air tools are not rocket science, surf the net for an exploded drawing, carefully disassemble it and clean the junk out of it. Lay the parts out on a clean surface in the order you take them apart, (yea, I know you think you will remember how it goes together, but you won't, not the first time) then re assemble and test.
I have a pretty good little sideline going, tool repair for the construction trades here locally. thease guy's are hard on tools, never do maintenance, and sometimes just give me the broke tools, after they replace them. A lot of them, mostly nail guns and staplers and hammer drills, just need cleaning, or the safety features re installed. (why they think the safety's need to be deactivated or broken off, I can't imagine,LOL) I keep a "loaner pool" for my good customers, and occasionally sell the rebuilt's. ANY gearhead, worthy of the name, can fix his own tools, go slow, don't force anything and enjoy the journey... RED